The Nightmares are the main antagonists of Link's Awakening. They are monsters that invaded the Wind Fish's dream world of Koholint. They seek to rule the island by preventing the Wind Fish from ever being awoken with the Instrument of the Sirens. To that end, eight of the Nightmares have taken each of the Instruments and hidden them within their lairs, accessible only by the Nightmare Keys hidden within their monster- and trap-filled labyrinths. The monsters were created by the Nightmares to prevent Link from awakening the Wind Fish. Most of these Nightmares are intelligent enough to speak to Link, the "outsider", and attempt to scare or warn him off of retrieving the Instruments, going so far as to reveal the true consequences of his actions: the destruction of the island and everything on it. Despite their warnings, Link retrieves each of the Instruments and even survives the final onslaught of the Shadow Nightmares at the Wind Fish's Egg, allowing him to reach the Wind Fish's resting place, play the Instruments, and awaken the sleeping deity.
- "Hoot! Young lad, I mean... Link , the hero! You have defeated the Nightmares! You have proven your wisdom, courage and power! ... ... ... ... As part of the Wind Fish's spirit, I am the guardian of his dream world... But one day, the Nightmares entered the dream and began wreaking havoc. Then you, Link , came to rescue the island... I have always trusted in your courage to turn back the Nightmares. Thank you, Link ... My work is done... The Wind Fish will wake soon. Good bye...Hoot!" — Owl (Link's Awakening DX)
- "We were born of nightmares... To take over this world, we made the Wind Fish sleep endlessly! If the Wind Fish doesn't wake up, this island will never disappear! We would have been the masters of this place... But you had to come here and disrupt our plans! Heh heh! You can never defeat us!!! Let's rumble!" — Shadow Nightmares (Link's Awakening DX)
- "You've got the Nightmare's Key! Now you can open the door to the Nightmare's Lair!" — N/A (Link's Awakening DX)
- "To avoid the destruction of the world, the Nightmares began creating monsters. So long as they do not relinquish the musical instruments of awakening, they can obstruct the hero." (Encyclopedia, Dark Horse Books, pg. 38)
- "Ssso...you are the outsssider, come to wake the Wind Fisssh... KEEE-HEE-HEEEH! I shall eat you!" — Slime Eel (Link's Awakening DX)
- "Eight Nightmares have hidden these magical, musical isntruments in their lairs. For each Nightmare that you defeat, you will win back one of these musical instruments." (Link's Awakening DX manual, pg. 13)
- "Okay, listen up! If the Wind Fish wakes up, everything on this island will be gone forever! And I do mean... EVERYTHING!" — Facade (Link's Awakening DX)